In collaboration with Professor Thomas Devlin of Hahnemann University in Philadelphia, PA an effort was made to evaluation a prostaglandin derivative called PGBx for its protective action against ischemic brain damage. This compound, isolated in the course of studies on stress, was found by earlier workers to protect vitro mitochondrial oxidative phosphorylation from hypoxia. We compared the survival of PGBx treated and untreated adult mongolian gerbils which had been subjected to 15 minutes of bilateral carotid occlusion. Although our first set of studies showed beneficial effects, repeated studies with new supplies of PGBx failed to show the effect even with major variations in dosage and time of dosage. Although this conclusion does not invalidate the metabolic studies which had shown other beneficial effects such as the restoration of oxidative phosphorylation in mitochondria exposed to hypoxia, further studies have been deferred.